1. Field of the Invention and Related Art Statement
The present invention relates to an ultrasonic endoscope apparatus comprising an endoscope having an insertion section which is insertable into a body under inspection, optical image observing means having an objective lens arranged in a distal end of the insertion section for forming an optical image of the body, and ultrasonic image observing means having an ultrasonic vibrating element provided in the distal end of the insertion section for forming an ultrasonic sectional image of the body.
The above mentioned ultrasonic endoscope apparatus for finding and diagonosing abnormal substances formed in a cavity wall of a living body, such as tumors formed on inner and outer walls of a stomach has been widely used. In such an ultrasonic endscope apparatus, the insertion section having the ultrasonic vibrating element installed in the distal end thereof is inserted into the cavity of the body, and a space between the distal end and the cavity wall is filled with an ultrasonic wave propagating medium, such as a physiological saline solution, by introducing the medium into a balloon arranged on the distal end of the insertion section. Then, the ultrasonic vibrating element is driven to effect the ultrasonic inspection. In this case, since a part of the cavity on which the ultrasonic wave is made incident could not be seen in the optical inspecting field of view, said part of the cavity could not be positively confirmed by the optical image, so that the ultrasonic image of the desired position of the cavity could not be obtained.
Japanese Utility Model Publication Kokai-shou 58-157,101 describes an ultrasonic endoscope apparatus in which a light emitting portion is provided at an end member of the insertion section. Upon using such an apparatus, a light beam emitted from the distal end of the insertion section is monitored from the outside of the body with the naked eye to confirm the direction in which the ultrasonic wave is emitted. German Patent Laid-open Publication p 33 36 803, discloses another known ultrasonic endoscope apparatus in which a light emitting element is provided on the ultrasonic probe and an emitted light beam is monitored by means of an endoscope inserted into a cavity of the body which is different from the cavity which is inspected by the ultrasonic endoscope apparatus. In these known ultrasonic endscope systems, the portion of the cavity which is inspected by the ultrasonic image is confirmed by monitoring the light beam which has passed through cavity walls or organs of the body.
Japanese Patent Publication Kokai-shou 58-133,232, describes a further known ultrasonic endoscope apparatus in which an image pick-up element and an ultrasonic vibrating element are mounted on the same rotating member so that the optical image and ultrasonic image always have a predetermined positional relationship. In such apparatus, after a position of the cavity has been confirmed by the optical image, the ultrasonic image may be obtained.
In the known ultrasonic endoscope systems described in Japanese Utility Model Publication Kokai-shou 58-157,101 and German Patent Publication P 33 36 803, the light beam could not be directly monitored, but is detected via the body. The position of the cavity on which the ultrasonic wave is made incident could not be determined precisely, and it is sometimes impossible to monitor the light beam at all depending upon the portion to be inspected.
In the known apparatus disclosed in Japanese Patent Publication Kokai-shou 58-133,232, since the ultrasonic vibrating element and image pick-up element are provided on opposite surfaces of the rotating member, it is impossible to monitor the optical image when the ultrasonic sectional image is monitored. Further, since it is required that the plane of the ultrasonic sectional image and the optical axis coincide with each other, this solution could not be applied to an endoscope having an inclined viewing axis.
Japanese Patent Publication Kokai-shou 63-3,616, discloses a further known ultrasonic endoscope apparatus in which a reflecting mirror is rotated and a light beam is emitted in synchronism with the rotation of the mirror to detect the part of the cavity under ultrasonic inspection. However, in this known apparatus the construction of the distal end of the insertion section tends to be complicated and the diameter of the insertion section is large.